Flora of North America species comparison

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Asclepias cordifolia

Asclepias welshii

heart-leaf milkweed, purple milkweed

Welsh's milkweed
Habit Herbs. Herbs.
Stems

1–20, ascending to spreading, unbranched, 25–100 cm, glabrous, glaucous, rhizomes absent.

1–20, erect to ascending, unbranched, 35–100 cm, densely tomentose to glabrate, not glaucous, rhizomatous.
Leaves

opposite, sessile, stipular colleters absent;

blade ovate to lanceolate, 3.5–11 × 1.8–8 cm, chartaceous, base cordate, clasping, margins entire, apex acute, mucronate, venation brochidodromous to eucamptodromous, surfaces glabrous, glaucous, margins minutely ciliate, laminar colleters absent.

subopposite to opposite (alternate), sessile or petiolate, stipular colleters absent;

petiole 0–8 mm, tomentose to glabrate;

blade oblong or obovate to oval or ovate, 4.5–14.5 × 2–8 cm, subsucculent, base rounded to cordate, margins entire, apex rounded or truncate to emarginate or acute, mucronate, venation brochidodromous, secondary veins orthogonal, surfaces tomentose to glabrate, margins eciliate, 0–10 laminar colleters.
Inflorescences

terminal, branched, sometimes also extra-axillary at upper nodes, pedunculate, 5–20-flowered;

peduncle 0.3–6.5 cm, apically sparsely pilose to glabrate, with few bracts.

extra-axillary from upper nodes, pedunculate, 22–80-flowered;

peduncle 2.5–6 cm, densely tomentose, with 1 caducous bract at the base of each pedicel.
Pedicels

16–37 mm, sparsely pilose.

10–15 mm, densely pilose to tomentose.
Flowers

erect to pendent;

calyx lobes elliptic to lanceolate, 3–5 mm, apex acute, pilose;

corolla red-violet, lobes reflexed with spreading tips, oval, 6–7 mm, apex acute, glabrous;

gynostegial column 1–1.5 mm;

fused anthers brown, cylindric, 1.5–2 mm, wings right-triangular, open at tip, apical appendages deltoid;

corona segments white, tinged pink to red-violet at base, sessile, tubular, 2–3 mm, exceeded by style apex, base saccate, apex truncate, oblique, glabrous, internal appendage absent;

style apex shallowly depressed, pink to red-violet.

erect to pendent;

calyx lobes linear, 5–6 mm, apex acute, densely pilose to tomentose;

corolla ochroleucous or tan to red-violet, lobes reflexed with spreading tips, oval to oblong, 5.5–6.5 mm, apex acute, densely tomentose abaxially, glabrous adaxially;

gynostegial column 1–1.5 mm;

fused anthers green to tan, obconic, 1.5 mm, wings triangular, widest at middle, closed, apical appendages ovate;

corona segments cream to ochroleucous, sometimes green at base, shiny, stipitate, tubular, dorsally flattened, 2.5–3.5 mm, exceeding style apex, apex truncate, glabrous, internal appendage falcate with acicular tip, exserted, sharply inflexed over style apex, glabrous;

style apex shallowly depressed, green.
Seeds

ovate, 8–9 × 5–7 mm, margin not winged, faces reticulate-rugulose;

coma 3–3.5 cm.

oval, 18–20 × 9–10 mm, margin winged, faces minutely rugulose;

coma 4–4.5 cm.
Follicles

erect on upcurved pedicels, lance-ovoid, 7.5–10.5 × 1.5–1.8 cm, apex long-acuminate, smooth, glabrous, glaucous.

pendulous on spreading pedicels, ellipsoid, 5–7 × 1.7–3 cm, apex acuminate, softly muricate, densely to thinly tomentose.
2n

= 22.

Asclepias cordifolia

Asclepias welshii
Phenology Flowering Mar–Jul(–Aug); fruiting Jun–Sep. Flowering May–Sep; fruiting Jun–Oct.
Habitat Hill­sides, canyons, ridge tops, streamsides, seeps, basalt, serpentine, gabbro, granite, shale, limestone, talus slopes, gravel, alluvium, oak woodlands, mixed ever­green, douglas-fir, pine, pine-oak, and riparian forests, chaparral, timberline meadows, grasslands. Active orange to red sand dunes, adjacent to pinyon-juniper and pine woodlands.
Elevation 50–2200(–2800) m. (200–7200(–9200) ft.) 1400–1900 m. (4600–6200 ft.)
Distribution
from FNA
CA; NV; OR
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; UT
[BONAP county map]
Discussion

Fresh leaves and stems of Asclepias cordifolia are often slightly or strongly colored bluish, grayish, or purplish. This is one of the few American species of Asclepias with cavitate corona segments that lack adaxial appendages. Such species were segregated along with diverse African species in Gomphocarpus R. Brown, a polyphyletic segregate (M. Fishbein et al. 2011; D. Chuba et al. 2017). Asclepias cordifolia is a distinctive species unlike any other within its range. It is phylogenetically and geographically isolated, although not highly derived morphologically. In Nevada, A. cordifolia is restricted to the Sierra Nevada, in Carson City, Douglas, and Washoe counties. Its range extends to northern California and southwestern Oregon.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

With respect to the number of populations, Asclepias welshii is the most endangered Asclepias in the flora area and is federally listed as threatened in the United States. Most of the populations are remote and relatively secure; however, the most accessible population in a Utah park has been subject to the impacts of off-road vehicle recreation. Leaves and stems of A. welshii emerge densely tomentose, but the lower portions of the plants become sand blasted and smooth as the season progresses. The species is strongly rhizomatous, as befits its shifting substrate. Seedlings and sprouts from rhizomes often bear narrowly linear leaves that differ so strongly from the foliage of more robust stems that they are not easily attributed to this species. Similar heterophylly is found in A. arenaria, A. erosa, and other milkweeds of sandy substrates.

(Discussion copyrighted by Flora of North America; reprinted with permission.)
Source FNA vol. 14. FNA vol. 14.
Parent taxa Apocynaceae > Asclepias Apocynaceae > Asclepias
Sibling taxa
A. albicans, A. amplexicaulis, A. angustifolia, A. arenaria, A. asperula, A. brachystephana, A. californica, A. cinerea, A. connivens, A. cryptoceras, A. curassavica, A. curtissii, A. cutleri, A. eastwoodiana, A. elata, A. emoryi, A. engelmanniana, A. eriocarpa, A. erosa, A. exaltata, A. fascicularis, A. feayi, A. hallii, A. hirtella, A. humistrata, A. hypoleuca, A. incarnata, A. involucrata, A. labriformis, A. lanceolata, A. lanuginosa, A. latifolia, A. lemmonii, A. linaria, A. linearis, A. longifolia, A. macrosperma, A. macrotis, A. meadii, A. michauxii, A. nummularia, A. nyctaginifolia, A. obovata, A. oenotheroides, A. ovalifolia, A. pedicellata, A. perennis, A. prostrata, A. pumila, A. purpurascens, A. quadrifolia, A. quinquedentata, A. rubra, A. rusbyi, A. ruthiae, A. sanjuanensis, A. scaposa, A. solanoana, A. speciosa, A. sperryi, A. stenophylla, A. subulata, A. subverticillata, A. sullivantii, A. syriaca, A. texana, A. tomentosa, A. tuberosa, A. uncialis, A. variegata, A. verticillata, A. vestita, A. viridiflora, A. viridis, A. viridula, A. welshii
A. albicans, A. amplexicaulis, A. angustifolia, A. arenaria, A. asperula, A. brachystephana, A. californica, A. cinerea, A. connivens, A. cordifolia, A. cryptoceras, A. curassavica, A. curtissii, A. cutleri, A. eastwoodiana, A. elata, A. emoryi, A. engelmanniana, A. eriocarpa, A. erosa, A. exaltata, A. fascicularis, A. feayi, A. hallii, A. hirtella, A. humistrata, A. hypoleuca, A. incarnata, A. involucrata, A. labriformis, A. lanceolata, A. lanuginosa, A. latifolia, A. lemmonii, A. linaria, A. linearis, A. longifolia, A. macrosperma, A. macrotis, A. meadii, A. michauxii, A. nummularia, A. nyctaginifolia, A. obovata, A. oenotheroides, A. ovalifolia, A. pedicellata, A. perennis, A. prostrata, A. pumila, A. purpurascens, A. quadrifolia, A. quinquedentata, A. rubra, A. rusbyi, A. ruthiae, A. sanjuanensis, A. scaposa, A. solanoana, A. speciosa, A. sperryi, A. stenophylla, A. subulata, A. subverticillata, A. sullivantii, A. syriaca, A. texana, A. tomentosa, A. tuberosa, A. uncialis, A. variegata, A. verticillata, A. vestita, A. viridiflora, A. viridis, A. viridula
Synonyms Acerates cordifolia, Gomphocarpus cordifolius
Name authority (Bentham) Jepson: Fl. W. Calif., 384. (1901) N. H. Holmgren & P. K. Holmgren: Brittonia 31: 110, fig. 1. (1979)
Web links 
Unless otherwise noted, all data comes from the online version of the Flora of North America, who have made most of their content available via a Creative Commons license (CC BY 4.0).



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